Methods of terminating electrical devices



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United States Patent 3,395,452 METHODS OF TERMINATING ELECTRICAL DEVICESWiley M. Hummel, Prophetstown, Ill., assignor to General ElectricCompany, a corporation of New York Original application Mar. 18, 1963,Ser. No. 265,665, now Patent No. 3,210,714, dated Oct. 5, 1965. Dividedand this application May 28, 1965, Ser. No. 459,781

7 Claims. (Cl. 29-621) ABSTRACT OF THE DISCLOSURE Method for making anelectrical connection between a relatively small diameter conductor,forming a coil winding, and a relatively large diameter lead conductor.The lead conductor is wrapped around a support, upon which the coilwinding is supported, and then twisted upon itself to firmly grasp thesupport. The small diameter conductor is then twisted around the leadconductor such that it lies within the valleys formed by the twisting ofthe large conductor. Subsequent steps may include welding and theapplication of a clip.

This application is a division of my co-pending application Ser. No.265,665, filed Mar. 18, 1963, now Patent No. 3,210,714, granted Oct. 5,1965. The present invention relates to electrical devices such asheating devices, and more particularly to methods for manufacturing andterminating resistance heating devices.

Accordingly, it is an object of my invention to provide a new andimproved method for efliciently connecting one end of a wire to aterminal.

A further object of my invention is to provide an improved method forterminating an electrical device.

A still further object of my invention is to provide an improved methodfor manufacturing an electrical heating device which is economicallyconstructed and eflicient in operation.

In carrying out my invention, in one form thereof I have provided animproved method of manufacturing and terminating a heating device whichincludes a relatively flat elongated support and a relatively thinheating conductor spirally wound upon the support. Near each end of thesupport a strip of flexible insulating tape is partially wrapped aroundsome of the end turns of the heating conductor. Each strip of tape alsocovers a loop in an end portion of the heating conductor, which loopextends longitudinally away from the end turns, and it is partiallywrapped around the support itself. A stranded bare conductor relativelythicker than the heating conductor is looped around the strip of tapenear each end of the support. The loop of this stranded conductor isdisposed transversely to the longitudinal axis of the support and itoverlies the longitudinal loop of the heating conductor. A shorter bareend of the stranded conductor is securely wound around an adjacentlonger length of the conductor to form a twisted junction that extendstransversely to the longitudinal axis of the support. By forming thistwisted junction, the stranded conductor is effectively secured to thesupport, and at the same time, the loop of the heating conductor is heldin engagement with the support by the loop of the stranded conductor.With such an arrangement, each bare end of the relatively thin heatingwire is wound into mechanical engagement with the twisted junction of anassociated stranded and looped conductor. Each twisted junction of thestranded conductor and the heating wire is thereupon welded to providepositive electrical engagement of the two conductors with each other.Such an arrangement provides a simplified and effective means and methodfor terminating an electrical heater.

Further aspects of my invention will become apparent hereinafter, andthe specification concludes with claims particularly pointing out anddistinctly claiming the subject matter which I regard as my invention.The invention, however, as to organization and method of utilization,together with further objects and advantages thereof, may best beunderstood by reference to the following description when taken inconjunction with the accompanying drawing in which:

FIGURE 1 is a perspective view of a mandrel mounted heating device whichis to be subsequently terminated in accordance with the presentinvention;

FIGURE 2 is a fragmentary perspective view of the device of FIGURE 1,after the attachment thereto of a stranded lead which serves as part ofa termination for the heating conductor;

FIGURE 3 is a fragmentary perspective view similar to FIGURE 2, andillustrating the mode of attachment of a welding clip to the juncture ofthe stranded lead and the heating conductor.

FIGURE 4 is a perspective view of a terminated heat ing device, inaccordance with my invention; and

FIGURE 5 is a sectional view taken generally along the line 55 of FIGURE4.

Referring first to FIGURE 1 of the drawing, there is illustrated anelectrical heating structure 1 which is mounted on an elongated mandrel3. The structure 1 generally comprises an elongated tube 5 of insulatingmaterial surrounding the mandrel 3 for the major portion thereof, and aheating conductor 7 spirally wound upon the tube 5.

As further shown in FIGURE 1, the mandrel 3 has a flat and rectangularcross section. Tube 5 is constructed of an insulating material such asTeflon, and is in the form of an extruded flat oval shaped sleeve havingrelatively thin walls which surround the mandrel 3, as shown in FIGURES1 and 5. The heating conductor 7 comprises a plurality of turns 8 ofinsulated wire which are precision wound on and supported by theinsulating tube 5, as shown in FIGURE 1.

Turning now to a significant aspect of my invention, which concerns anew and improved method for terminating the heating conductor 7, asshown in FIGURE 1 each end portion of the heating conductor 7 is bentover and away from the longitudinal center of the heating conductor, ina direction generally parallel to the longitudinal axis of the mandrel3. A strip of flexible insulating tape 9, such as for example,fiberglass tape is then pressed initially into engagement with theparallel conductor sections of several of the end turns of the heatingconductor 7, and the adjacent portion of the tube 5 so that it coversand positions the bent over longitudinal section 11 of the conductornear its end. The end portion of the conductor 7 is then looped over at13 and doubled back upon itself by extending a portion 15 back towardthe center of the conductor in a direction generally parallel to thelongitudinal axis of the mandrel 3. The doubled over portion 15 is thenon the outer surface of the beginning part of tape 9. Tape 9 is thenwrapped completely around the end turns, and the adjacent part of tube 5and overlapped upon the doubled over portion 15 of the conductor. Thus,as shown in FIGURE 1, the tape 9 overlaps itself in such a manner thatthe starting portion of tape 9 is threaded through the loop 13, and thedoubled over portion 15 of the conductor wire 7 is arranged between anouter surface of the tape 9 and an overlapped part of the tape 9.

For terminating the stripped ends 7a of the heating conductor 7, asshown in FIGURES 2 and 4, a pair of stranded conductors 17 are utilized.As illustrated in FIGURE 2, conductor 17 is substantially bare, is firstlooped around tape 9, and is positioned adjacent to a shoulder 21 oftape 9. Shoulder 21 is formed by stretching tape 9 at the end-most turnof the heating conductor 7 (Le, between the end-most turn and theadjacent uncovered surface of the tube 5). T e loop 19 of stranded bareconductor 17 is thus positioned around the taped section of the device(as shown in FIGURE 2) just beyond the last turn of heater conductor 7and a relatively short end portion 23 of the stranded conductor 17 isthereupon securely twisted around an adjacent portion 25 of the longerlength of the stranded conductor 17.

As shown in FIGURE 2, when the shorter end 23 of the stranded conductor17 is twisted, there is formed a tightly twisted junction 27 of theshorter portion 23 of conductor 17 with the longer portion 25 thereof.By means of the twisted junction 27, the loop 19 is tightly securedaround the folded over tape 9. Since the loop 19 of conductor 17 isarranged in transverse relationship to the longitudinal loop of theheater conductor 7, it also compresses the looped end of the heatingconductor 7 into engagement with the tube 5. It will thus be understoodthat by twisting the stranded conductor 17, this conductor has beensecurely arranged upon the tube 5 and tape 9, and at the same time thelooped end of the insulated heating conductor 7 has been additionallysecured into compressive engagement with its supporting tube 5.

After the twisted junction 27 has been formed upon the strandedconductor 17, the stripped end 7a of heating conductor 7 is then doubledback again and wound around the twisted junction 27, in the mannerillustrated in FIG- URE 2. More particularly, the stripped end 7a ofheating conductor 7 is preferably Wound around the twisted junction inthe same direction as the direction of twisting of shorter end 23 ofconductor 17, and at substantially the same pitch as the twistedjunction so that the turns 7b of the stripped end 7a are approximatelydisposed between adjacent turns 17a of the twisted junction of theconductor 7. It will thus be seen that I have provided a simplifiedmeans for facilitating the mechanical connection and cooperation of theconductor 7 of relatively small diameter with a stranded lead 17 oflarger diameter.

After the stripped end 7a has been wound into mechanical engagement withthe twisted junction 27 of the conductor 17, as suggested by FIGURE 3, acrimping clip 29 is thereupon mechanically crimped into engagement withthe twisted junction 27, and the turns 7b of the stripped end 7a ofheating conductor 7 (see also FIGURE 4). Preferably, in the illustratedheating device, the clip 29 is placed as close as possible to the tape 9and engulfs a substantial portion of the twisted junction. As shown inFIGURE 4, the clip 29, the twisted junction 27, and stripped turns 7b ofthe heating conductor 7 are all then welded together to form a good andpositive electrical connection and termination for each end of theheating conductor 7.

While the terminated heating device, as shown in FIG- URE 4, ispositioned on a supporting mandrel 3, it will be understood by thoseskilled in the art, that the mandrel 3 may be readily removed from tube5, and an elongated bimetallic member (not shown) or some otherthermally responsive member may be extended through the tube to providea thermal timing device.

It will now, therefore, be seen that my new and improved method formanufacturing and terminating electrical devices, as herein illustratedfor an electrical resistance heater, are both efiicient andadvantageous. In view of the simplified construction of this device andits eflicient mode of termination, it has been found to be veryeconomical to manufacture.

While in accordance with the patent statutes I have described what atpresent is considered to be the preferred embodiment of my invention itwill be obvious to those skilled in the art that various changes andmodifications may be made therein without departing from my invention,and I, therefore, aim in the following claims to 4 v. cover all suchequivalent variations as fall within the true spirit and scope of thisinvention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A method for making an electrical connection comprising the steps oflooping an end portion of afirst conductor around a support, twisting anend section of the first conductor around an adjacent section thereof toform a tight loop of the end portion mechanically secured to the supportand a twisted junction of bare wire of the end section of the firstconductor and the adjacent section, winding the bare end of a secondconductor around the twisted junction of the first conductor, and fusingthe bare end of the second conductor to the twisted junction of thefirst conductor.

2. A method for making an electrical connection comprising the steps oflooping an end portion of a stranded first conductor around a support,twisting the free end of the first conductor around an adjacent sectionthereof to form a twisted junction of bare wire of the free end andadjacent section of the first conductor and a tight loop of the endportion mechanically secured to the support, winding the bare end of asecond conductor around the twisted junction of the first conductor, andwelding the bare end of the second conductor to the twisted junction ofthe first conductor.

3. A method for making an electrical connection comprising the steps ofpositioning a looped end portion of a first conductor around a support,twisting the free end of the first conductor around an adjacent sectionthereof to form a tight loop of the end portion mechanically secured tothe support and a twisted junction of bare wire of the free end andadjacent section of the first conductor, and winding the bare end of asecond conductor of less diameter than said first conductor around thetwisted junction of the first conductor, the second conductor beingwound around the first conductor so that at least some of the turns ofthe second conductor are disposed between adjacent turns of the twistedjunction of the first conductor, and fusing the turns of the secondconductor to the twisted junction of the first conductor.

4. A method for making an electrical device comprising the steps ofwinding a first conductor on an elongated support around thelongitudinal axis of said support, forming a first loop in an endportion of said first conductor, said first loop extending in adirection generally parallel to the axis of said support and disposed incontiguity thereto, forming a second loop in an end portion of a secondconductor, said second loop being arranged in trans verse fashion aroundsaid support and traversing said first loop, twisting the free end ofthe second conductor around an adjacent section thereof to tighten saidsecond loop into mechanical engagement with said support and to compresssaid first loop of said first conductor into secure engagement with saidsupport, the twisting of the free end of said second conductor forming atwisted junction of bare wire of said second conductor, and winding thebare end of the end portion of said first conductor around the twistedjunction of said second conductor.

5. A method for making an electrical device comprising the steps ofwinding a first conductor on an elongated support around thelongitudinal axis of said support, forming a first loop in an endportion of said first conductor, said first loop extending in adirection generally parallel to the axis of said support and disposed incontiguity thereto, forming a second loop in an end portion of a secondconductor, said second loop being arranged in transverse fashion aroundsaid support and traversing said first loop, twisting the free end ofthe second conductor around an adjacent section thereof to tighten saidsecond loop into mechanical engagement with said support and to compresssaid first loop of said first conductor into secure engagement with saidsupport, the twisting of the free end of said second conductor forming atwisted junction of bare wire of said second conductor, winding the bareend of the end portion of said first conductor around the twistedjunction of said second conductor, and welding the bare end of saidfirst conductor to the twisted junction of said second conductor.

6. A method for making an electrical device comprising the steps ofwinding a first conductor on an elongated support around thelongitudinal axis of said support, forming a first loop in an endportion of said first conductor, said first loop extending in adirection generally parallel to the axis of said support and disposed incontiguity thereto, forming a second loop in an end portion of a secondconductor, said second loop being arranged in transverse fashion aroundsaid support and traversing said first loop, twisting the free end ofthe second conductor around an adjacent section thereof to tighten saidsecond loop into mechanical engagement with said support and to compresssaid first loop of said first conductor into secure engagement with saidsupport, the twisting of the free end of said second conductor forming atwisted junction of bare wire of said second conductor, winding the bareend of the end portion of said first conductor around the twistedjunction of said second conductor, clamping the bare end of said firstconductor to said twisted junction adjacent said second loop, andwelding the bare end of said first conductor to the twisted junction ofsaid second conductor.

7. A method for making an electrical device comprising the steps ofwinding a first conductor on an elongated support around thelongitudinal axis of said support, forming a first loop in an endportion of said first conductor, said first loop extending in adirection generally parallel to the axis of said support and disposed incontiguity thereto, threading a strip of flexible insulating tapethrough said first loop and wrapping said strip in overlapped fashionaround said loop and at least a portion of said first conductor adjacentsaid loop, forming a second loop in an end portion of a secondconductor, said second loop being arranged in transverse fashion aroundsaid support and traversing said first loop, twisting the free end ofthe second conductor around an adjacent section thereof to tighten saidsecond loop into mechanical engagement with said support and to compresssaid first loop of said first conductor into secure engagement with saidsupport, the twisting of the free end of said second conductor forming atwisted junction of bare wire of said second conductor, winding the bareend of the end portion of said first conductor around the twistedjunction of said second conductor, clamping the bare end of said firstconductor to said twisted junction adjacent said second loop, andwelding the bare end of said first conductor to the twisted junction ofsaid second conductor.

References Cited UNITED STATES PATENTS CHARLIE T. MOON,

J. CLINE, Assistant Examiner.

Primary Examiner.

